1. Field of the Invention
The present invention relates to an image sensor, and more particularly, to a CMOS image sensor and a method of manufacturing the same.
2. Description of the Related Art
A CMOS image sensor is a semiconductor device with a plurality of photodiodes integrated therein, and each of the photodiodes is a sensor for converting incident light into an electrical signal to detect an image of a target object. The CMOS image sensors have been developed to be mounted to portable, hand-held, personal compact devices such as camera phones and digital cameras, so there is limitation to their size.
In a common image sensor, the smallest unit to detect the light is a pixel. The image sensor includes a plurality of pixels. The pixel includes a photodiode, a drive device for driving the interested photodiode, and other devices. The pixels correspond to the photodiodes one-to-one, and the ratio of the light receiving area of the photodiode to the image sensor surface area per pixel is referred to as the “fill factor.” The fill factor of a common image sensor is about 20%. Therefore, the fill factor is a standard for photosensitivity of the image sensor.
In order to improve the photosensitivity of the image sensor in the restricted space, it is necessary to increase the number of pixels to be integrated, and it is necessary to expand the light receiving area of the photodiode occupying the pixel to the largest possible extent.
A proposed measure for increasing the fill factor of the sensor involves locating, for each pixel, a micro lens at a position corresponding to the light receiving area to collect light onto the photodiode.
However, light not received by the photodiodes through the micro lenses may cause cross talk. This interference between unnecessary light beams blurs colors in the image sensor.